Even if you've never seen an episode of the old TV show, there are still three things you surely know about the Lone Ranger: he wears a mask, he has a best friend named Tonto, and he carries silver bullets.

The reasons behind the first two are obvious: he wears a mask to obscure his identity, and his trusted pal Tonto is a skilled scout and valuable resource. But why on earth would someone cast bullets out of silver?

Well, the upcoming big-budget movie version of "The Lone Ranger" has an explanation that is slightly different than the one from the character's origins. Check out the film's exclusive final trailer, premiering right here on Yahoo! Movies, and keep reading to learn why the Western icon needs such precious ammunition. Watch the exclusive final trailer for 'The Lone Ranger':

Originally created for the radio in 1933, the Lone Ranger became a phenomenon on TV in the series that begin in 1949. As envisioned by creators Fran Striker and George W. Trendle, the Ranger lived by the highest moral standards, and he was distinct from other Western heroes in that he only ever shot to disarm, not to kill. That's where the silver bullets came in. As a symbol of purity, using silver was a reminder of the high cost that came with firing a gun. (The guy is so obsessed with the stuff he even named his horse "Silver.")

For the new movie, the characters of both the Lone Ranger and Tonto have expanded backstories, and it offers a new rationale for the silver bullets. In this story, John Reid (played by Armie Hammer) is actually a lawyer who returns to his dusty hometown to take the job of county prosecutor. He believes in by-the-book law and order, which puts him at odds with his older brother Dan Reid (James Badge Dale), who is a tough Texas Ranger like their father was.

After John witnesses the escape of the wanted criminal Butch Cavendish (William Fichtner), he volunteers to join Dan and his band of Rangers to hunt down Cavendish. But they are ambushed by the gang and everyone but John is killed.

As it happens, though, someone else is after Cavendish: the Comanche scout Tonto (Johnny Depp). He rescues John and nurses him back to health, believing he is a great warrior sent to help him. Since Cavendish believes John died with his brother, Tonto suggests he wear a mask to hide his identity (and protect Dan's widow Rebecca, who John also loves).

For Tonto, Cavendish is more than just a villain, he's a powerful evil presence. Tonto believes he is a "Wendigo," which is a cannibalistic demon in some Native American legends that can transform into or possess the body of a human. Tonto tells John Reid that being a Wendigo, Cavendish cannot be killed by normal means. Like other creatures in mythology — werewolves and vampires, for example — the purity of silver can break the evil magic, so Tonto gives the Ranger a single silver bullet. He'll only have one shot at ridding the West of this dangerous, and maybe even supernatural, criminal.

Of course, getting to Cavendish is going to be its own adventure, filled with fist-fights, horse chases, and train wrecks. And since this new film is from the writers, producer, and director of the original "Pirates of the Caribbean," you know it's going to be an epic ride.